This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. High resolution spectroscopy is often fundamentally limited in accuracy by the spectral linewidth of the excitation laser. Observing spectral shifts in emission light due to opto-acoustic interactions requires sub-GHz bandwidth lasers. However, Ti:Sapphire lasers operating in broadband mode typically produce a bandwidth on the order of 1 GHz or more. By inserting an etalon in the laser cavity, the Ti:Sapphire laser linewidth can be narrowed to the range of 10 MHz with 60~70% efficiency. Further reduction in linewidth to the range of 500 kHz can be achieved with minimal loss by employing active frequency control.